The present invention generally concerns compressors of the type employed in airtight refrigerating units in household and similar apparatus, and particularly valve systems used therein.
The numerous governmental regulations, such as the Directives of the European Union, which impose increasingly strict limits on the efficiency of household appliances, have become a ever more critical factor in refrigeration design. Energy consumption by refrigeration appliances is largely dependent upon the overall yield of the refrigerating unit, which in turn depends not only on the efficiency of the electric motor that operates it and the mechanical yield of the compressor itself, but also on the volumetric yield of the compressor. The valve system of the compressor plays a significant part in this determination.
With regard to aspiration type valves, which are of the thin-plate or reed type, it is well known how to fabricate them, using a process involving shearing steel ribbon and successive machining, so as to provide valves that are flush with a compressor""s valve plate. The anchoring portion of the valve is permanently sealed, by at least one flat sealing gasket, between the plate and the cylinder body. This method is, however, less cost efficient than traditional valve systems due to the high tolerance requirements for the aspiration valve resulting in a less reliable valve and a higher cost of manufacture.
Another known method is fabricating an aspiration valve such that its anchoring portion includes creased tabs, whose edges are anchored in corresponding indentations in the valve plate, such as is disclosed in patent application WO 99/30037. While the sensitivity of the valve to tolerance is less important, this method instead requires a very precise machining of the body of the compressor to accommodate the anchoring portion of the valve (excluding the edges of the tabs) and of the head of the piston to accommodate the main portion of the valve in such a way as to minimize the wasted volume of the compressor.
It would therefore be desirable to devise an improved aspiration valve system for such refrigeration compressors, so as to increase the volumetric yield of the compressor, and consequently the overall yield of the airtight unit, while also simplifying the manufacturing process.
Provided according to one aspect of the present invention is a compressor for an airtight refrigerating unit comprising a cylinder body, a compressor head, a valve plate held between the cylinder body and the compressor head with the interposition of a first flat sealing gasket and a second flat sealing gasket, and a thin-sheet aspiration valve associated with an aspiration hole provided on the valve plate. The entire aspiration valve is substantially accommodated within a recessed area provided on a surface of the valve plate that is directed toward the cylinder body.
According to another aspect of the present invention, the recessed area comprises a main area which accommodates a main portion of the aspiration valve, and at least one other area of indentation having a depth greater than the depth of the main area. This other indentation is capable of accommodating an anchoring portion of the aspiration valve.
According to yet another aspect of the present invention, the aspiration valve does not substantially protrude into the cylinder, thus potentially providing an increase in usable cylinder volume and in turn an increase in overall compressor efficiency.
According to still another aspect of the present invention, the aspiration valve is a generally T-shaped flat tongue. This flat tongue comprises an elongated main portion having a free rounded end that is capable of sealing the aspiration hole of the valve plate, and a transverse anchoring portion that comprises at least one creased tab.